Method of controlling particle absorption on a wafer sample being inspected by a charged particle beam imaging system

ABSTRACT

A method of controlling particle absorption on a wafer sample being inspected by a charged particle beam imaging system prevents particle absorption by grounding the wafer sample and kept electrically neutral during the transfer-in and transfer-out process.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to controlling particle absorption on awafer sample, and more particularly to controlling particle absorptionon a wafer sample being inspected by a charged particle beam imagingsystem.

2. Description of the Prior Art

As electronic devices become smaller in size, the processing techniquethereof becomes more microscopic. Charged particle beam imaging willlikely become one of the critical technologies in advanced semiconductormanufacture. Charged particle beam imaging tools, which includeconventional scanning electron microscopes (SEMs) have a much higherresolution than optical tools and are able to detect smaller sizedefects.

Particles such as dust in atmosphere influence the characteristics oryield of manufactured electronic devices significantly. Due to this,elimination of particles during the manufacturing process is a veryimportant factor. In a microscopic circuit, since the sizes of particlesare as large as or even larger than the distance between metal wires,yield (ratio of source material to product) is degraded when particlesare adhered to the wafer causing short circuits or other problems.

Conventional methods for removing particles from, for example, a waferchuck in a testing apparatus include the use of an air gun or nozzle toblow particles away from the chuck. However, this method is onlypartially effective in removing the particles from the chuck, especiallythose carrying charges.

Hence, how to control particle absorption on a wafer sample within acharged particle beam imaging system is now urgently needed to target.

SUMMARY OF THE INVENTION

The present invention is directed to a method of controlling particleabsorption on a wafer sample being inspected by a charged particle beamimaging system. The disclosed method prevents particle absorption bygrounding the wafer sample to keep it electrically neutral during thetransfer-in and transfer-out process of the wafer.

According to an aspect, a method of controlling particle absorption on awafer sample within a charged particle beam imaging system in anembodiment includes performing a transfer-in process to transfer thewafer sample from a wafer sample storage onto a support member for acharged particle beam imaging, the wafer sample storage being configuredfor pre-imaging and post-imaging storage of the wafer sample, thesupport member being configured for supporting the wafer sample thereonduring the charged particle beam imaging, the support member beingequipped with a securing unit for securing and un-securing the wafersample on the support member; performing the charged particle beamimaging of the wafer sample; and performing a transfer-out process totransfer the wafer sample from the support member to said wafer samplestorage, wherein during the transfer-in and transfer-out process, thewafer sample is kept electrically neutral by grounding the wafer sample.

According to another aspect, a computer readable medium encoded with acomputer program for controlling particle absorption on a wafer sampleduring charged particle beam imaging includes transferring, using afirst sample handling member, the wafer sample from a wafer samplestorage onto a surface of a pre-aligner, the wafer sample storage beingconfigured for pre-imaging and post-imaging storage of the wafer sample,the pre-aligner being configured for adjusting an angle of the wafersample; transferring, using the first sample handling member, the wafersample from the pre-aligner onto a platform of a loading chamber, theloading chamber being configured for preparing the wafer sample for thecharged particle beam imaging; picking the wafer sample within theloading chamber using a second sample handling member; transferring,using a third sample handling member, the wafer sample from the secondsample handling member onto a surface of a support member disposedwithin an inspection chamber for supporting the wafer sample thereonduring the charged particle beam imaging, the support member beingequipped with a securing unit for securing and un-securing the wafersample on the support member; securing the wafer sample on the supportmember using the securing unit; performing the charged particle beamimaging of the wafer sample; un-securing the wafer sample; picking thewafer sample from the support member using the third sample handlingmember; transferring, using the second sample handling member, the wafersample from the third sample handling member onto the platform of theloading chamber; and transferring, using the first sample handlingmember, the wafer sample from the loading chamber into the wafer samplestorage, wherein at any given time point other than the charged particlebeam imaging step, the wafer sample is kept electrically neutral bygrounding the first, second and third sample handling members, thepre-aligner, the loading chamber, the support member and the securingunit.

According to yet another aspect, a charged particle beam imaging systemof a wafer sample includes a charged particle beam generator, acondenser lens module, a probe forming objective lens module, a chargedparticle beam deflection module, a secondary charged particle detectormodule, an image forming module, and a particle contaminationcontroller. The charged particle beam generator is configured forgenerating a primary charged particle beam; the probe forming objectivelens module is configured for focusing condensed the primary chargedparticle beam into a charged particle beam probe; the charged particlebeam deflection module for scanning the charged particle beam probeacross a surface of the wafer sample; the secondary charged particledetector module is configured for detecting charged particles generatedfrom the wafer sample surface when being bombarded by the chargedparticle beam probe, and whereby generating a secondary charged particledetection signal accordingly; and the image forming module electricallycoupled with the secondary charged particle detector module forreceiving the secondary charged particle detection signal from thesecondary charged particle detector module and forming at least onecharged particle microscopic image. The particle contaminationcontroller is coupled with a first sample handling member, a secondsample handling member and a third sample handling member fortransferring the wafer sample, a wafer sample storage for pre-imagingand post-imaging storage of the wafer sample, a pre-aligner foradjusting an angle of the wafer sample, a loading chamber for preparingthe wafer sample for the charged particle beam imaging, and a supportmember disposed within an inspection chamber for supporting the wafersample thereon during the charged particle inspection, the supportmember being equipped with a securing unit for securing and un-securingthe wafer sample on the support member. The particle contaminationcontroller includes a computer readable medium encoded with a computerprogram for controlling particle absorption on a wafer sample duringcharged particle beam imaging. The computer program executes stepsincluding transferring, using a first sample handling member, the wafersample from a wafer sample storage onto a surface of a pre-aligner, thewafer sample storage being configured for pre-imaging and post-imagingstorage of the wafer sample, the pre-aligner being configured foradjusting an angle of the wafer sample; transferring, using the firstsample handling member, the wafer sample from the pre-aligner onto aplatform of a loading chamber, the loading chamber being configured forpreparing the wafer sample for the charged particle beam imaging;picking the wafer sample within the loading chamber using a secondsample handling member; transferring, using a third sample handlingmember, the wafer sample from the second sample handling member onto asurface of a support member disposed within an inspection chamber forsupporting the wafer sample thereon during the charged particle beamimaging, the support member being equipped with a securing unit forsecuring and un-securing the wafer sample on the support member;securing the wafer sample on the support member using the securing unit;performing the charged particle beam imaging of the wafer sample;un-securing the wafer sample; picking the wafer sample from the supportmember using the third sample handling member; transferring, using thesecond sample handling member, the wafer sample from the third samplehandling member onto the platform of the loading chamber; andtransferring, using the first sample handling member, the wafer samplefrom the loading chamber into the wafer sample storage, wherein at anygiven time point other than the charged particle beam imaging step, thewafer sample is kept electrically neutral by grounding the first, secondand third sample handling members, the pre-aligner, the loading chamber,the support member and the securing unit.

Other advantages of the present invention will become apparent from thefollowing description taken in conjunction with the accompanyingdrawings wherein are set forth, by way of illustration and example,certain embodiments of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing aspects and many of the accompanying advantages of thisinvention will become more readily appreciated as the same becomesbetter understood by reference to the following detailed description,when taken in conjunction with the accompanying drawings, wherein:

FIG. 1 to FIG. 3 are flow charts illustrating an embodiment of thepresent invention; and

FIG. 4 and FIG. 5 are schematic diagrams illustrating a charged particlebeam imaging system of a wafer sample according to another embodiment ofthe present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Refer to FIG. 1 in conjunction with FIG. 4. FIG. 1 illustrates a flowchart of a method of controlling particle absorption on a wafer samplewithin a charged particle beam imaging system illustrated in FIG. 4 ofan embodiment according to the present invention. FIG. 1 begins withperforming a transfer-in process to transfer the wafer sample 100 from awafer sample storage 10 onto a support member 70 for a charged particlebeam imaging (S11), in which the wafer sample storage 10 is configuredfor pre-imaging and post-imaging storage of the wafer sample 100, thesupport member 70 is configured for supporting the wafer sample 100thereon during the charged particle beam imaging, the support member 70is equipped with a securing unit 80 for securing and un-securing thewafer sample 100 on the support member 70. Next, perform a chargedparticle beam imaging of the wafer sample 100 (S12). Lastly, perform atransfer-out process to transfer the wafer sample 100 from the supportmember 70 to the wafer sample storage 10 (S13). It is noted that thewafer sample 100 is kept electrically neutral by grounding the wafersample 100 during the transfer-in (S11) and transfer-out process (S13).

In one embodiment, the transfer-in process S11 and the transfer-outprocess S13 include transferring the wafer sample 100 between at leastone work chamber using at least one sample handling device, in which thework chamber is configured for preparing the wafer sample 100 for thecharged particle beam imaging, or for the charged particle beam imagingstep S12 to be performed therewithin. The sample handling device and atleast one portion of the work chamber is in contact with the wafersample 100. This at least one portion of the work chamber is groundedanytime during the transfer-in process S11 and the transfer-out processS13.

FIG. 2 is a flow chart illustrating the further detailed process of thetransfer-in process S11 illustrated in FIG. 1. Referring to FIG. 2 andFIG. 4, the transfer-in process S11 begins with transferring, using afirst sample handling member 20, the wafer sample 100 from the wafersample storage 10 onto the surface of a pre-aligner 30, in which thepre-aligner 30 is configured for adjusting an angle of the wafer sample100 (S21). Next, transfer, using the first sample handling member 20,the wafer sample 100 from the pre-aligner 30 onto a platform of aloading chamber 40 (S22), in which the loading chamber 40 is configuredfor preparing the wafer sample 100 for the charged particle beamimaging. The wafer sample 100 is then grabbed by a second samplehandling member 50 within the loading chamber 40 (S23), and then pickedand transferred from the second sample handling member 50 by a thirdsample handling member 60 onto the surface of the support member 70disposed within an inspection chamber (S24). Lastly, the wafer sample100 on the support member 70 is secured by the securing unit 80 (S25),so as for the charged particle beam imaging step to be performedsubsequently. It is noted that the wafer sample 100 is kept electricallyneutral by grounding the first, second and third sample handling members(20, 50, 60), the pre-aligner 30, the platform of the loading chamber40, the support member 70 and the securing unit 80 anytime during thetransfer-in process. In a preferred embodiment, any one of the first,second and third sample handling member (20, 50, 60), the pre-aligner30, the platform of the loading chamber 40, the support member 70 andthe securing unit 80 has an electrical resistivity of 10⁵ to 10⁹ohms-cm, or less than 10⁵ ohms-cm. In an embodiment, the securing unit80 includes an electrostatic chuck (e-chuck).

FIG. 3 is a flow chart illustrating the further detailed process of thetransfer-out process S13 illustrated in FIG. 1. In transfer-out processS13, the wafer sample 100 on the support member 70 is released orun-secured from the securing unit 80 after the step of the chargedparticle beam imaging (S31). Next, the wafer sample 100 is picked by thethird sample handling member 60 from the support member 70 (S32),transferred to the second sample handling member 50, and then put ontothe platform of the loading chamber 40 (S33) by the second samplehandling member 50. Lastly, transfer, using the first sample handlingmember 20, the wafer sample 100 from the loading chamber 40 into thewafer sample storage 10 (S34). It is noted that in the entiretransfer-out process the wafer sample 100 is kept electrically neutralall the time by grounding the first, second and third sample handlingmembers (20, 50, 60), the platform of the loading chamber 40, thesupport member 70 and the securing unit 80. In a preferred embodiment,the first, second and third sample handling members (20, 50, 60), thepre-aligner 30, the platform of the loading chamber 40, the supportmember 70 and the securing unit 80 have an electrical resistivity of 10⁵to 10⁹ ohms-cm, or less than 10⁵ ohms-cm. In an embodiment, the securingunit 80 includes an electrostatic chuck (e-chuck).

In an embodiment, the wafer sample storage 10 includes one selected froma group consisting of the following, or any combination thereof:cassette, standard mechanical interface (SMIF), front opening unifiedpod (FOUP); the first sample handling member 20 includes a robot endeffecter; the second sample handling member includes a vacuum arm; thethird sample handling member 60 includes at least one projectionsarranged on the support member 70 and upon which the wafer sample 100 isseated; and the loading chamber 40 includes a load lock.

Referring to FIG. 4 and FIG. 5, a charged particle beam imaging systemof a wafer sample according to an embodiment of the present invention isillustrated. As shown in FIG. 5, a charged particle beam imaging systemincludes a charged particle beam generator 110, a condenser lens module120, a probe forming objective lens module 130, a charged particle beamdeflection module 150, a secondary charged particle detector module 170,an image forming module 180, and a particle contamination controller220.

The charged particle beam generator 110 is configured for generating aprimary charged particle beam; the condenser lens module 120 forcondensing said primary charged particle beam; the probe formingobjective lens module 130 is configured for focusing condensed theprimary charged particle beam into a charged particle beam probe 140;the charged particle beam deflection module 150 is configured forscanning the charged particle beam probe 140 across a surface of thewafer sample 100; the secondary charged particle detector module 170 isconfigured for detecting charged particles 160 generated from thesurface of wafer sample 100 when being bombarded by the charged particlebeam probe 140, and whereby generating a secondary charged particledetection signal accordingly; and the image forming module 180electrically coupled with the secondary charged particle detector module170 is configured for receiving the secondary charged particle detectionsignal from the secondary charged particle detector module 170 andforming at least one charged particle microscope image.

As shown in FIG. 4, the particle contamination controller 220 is coupledwith the first sample handling member 20, the second sample handlingmember 50 and the third sample handling member 60 for transferring thewafer sample 100, the wafer sample storage 10 for pre-imaging andpost-imaging storage of the wafer sample 100, the pre-aligner 30 foradjusting an angle of the wafer sample 100, the loading chamber 40 forpreparing the wafer sample 100 for the charged particle beam imaging,and the support member 70 disposed within an inspection chamber forsupporting the wafer sample 100 thereon during the charged particleinspection, the support member 70 being equipped with a securing unit 80for securing and un-securing the wafer sample 100 on the support member70.

The particle contamination controller 220 includes a computer readablemedium encoded with a computer program for controlling particleabsorption on the wafer sample 100 during charged particle beam imaging.Referring to FIG. 1 to FIG. 3, the computer program performs the samesteps in the above-mentioned embodiment, including steps S21˜25, S12,and S31˜34.

It is noted that at any given time point other than the charged particlebeam imaging step S12, the wafer sample 100 is kept electrically neutralby grounding the first, second and third sample handling members (20,50, 60), the pre-aligner 30, the loading chamber 40, the support member70 and the securing unit 80. In a preferred embodiment, the first,second and third sample handling members (20, 50, 60), the pre-aligner30, the platform of the loading chamber 40, the support member 70 andthe securing unit 80 have an electrical resistivity of 10⁵ to 10⁹ohms-cm, or less than 10⁵ ohms-cm.

In an embodiment, the wafer sample storage 10 includes one selected froma group consisting of the following, or any combination thereof:cassette, standard mechanical interface (SMIF), front opening unifiedpod (FOUP); the first sample handling member 20 includes a robot endeffecter; the second sample handling member 50 includes a vacuum arm;the third sample handling member 60 includes at least one projectionsupon the wafer sample is seated; and the loading chamber 40 includes aload lock.

To sum up the foregoing descriptions, the present invention controlsparticle absorption on a wafer sample within a charged particle beamimaging system and is achieved by keeping the wafer sample electricallyneutral by grounding the wafer sample all the time except for during theactual inspection.

While the invention is susceptible to various modifications andalternative forms, a specific example thereof has been shown in thedrawings and is herein described in detail. It should be understood,however, that the invention is not to be limited to the particular formdisclosed, but to the contrary, the invention is to cover allmodifications, equivalents, and alternatives falling within the spiritand scope of the appended claims.

1. A method of controlling particle absorption on a wafer sample withina charged particle beam imaging system, comprising: performing atransfer-in process to transfer said wafer sample from a wafer samplestorage onto a support member for a charged particle beam imaging, saidwafer sample storage being configured for pre-imaging and post-imagingstorage of said wafer sample, said support member being configured forsupporting said wafer sample thereon during said charged particle beamimaging, said support member being equipped with a securing unit forsecuring and un-securing said wafer sample on said support member,wherein said transfer-in process comprises: transferring, using a firstsample handling member, said wafer sample from said wafer sample storageonto a surface of a pre-aligner, said pre-aligner being configured foradjusting an angle of said wafer sample; transferring, using said firstsample handling, member, said wafer sample from Said pre-aligner onto aplatform of a loading chamber, said loading chamber being configured forpreparing said wafer sample for said charged particle beam imaging;picking said wafer sample within said loading chamber using a secondsample handling member; transferring, using a third sample handlingmember, said wafer sample from said second sample handling member onto asurface of said support member disposed within an inspection chamber;and securing said wafer sample on said support member using saidsecuring unit, so as for said charged particle beam imaging step to beperformed subsequently, wherein at any given time point during saidtransfer-in process, said wafer sample is caused to be electricallyneutral by grounding said first, second and third sample handlingmembers, said pre-aligner, said loading chamber, support member and saidsecuring unit; performing said charged particle beam imaging of saidwafer sample; and performing a transfer-out process to transfer saidwafer sample from said support member to said wafer sample storage,wherein during said transfer-in and transfer-out process, said wafersample is kept electrically neutral by grounding said wafer sample. 2.The method of claim 1, wherein said transfer-in and transfer-out processcomprises transferring said wafer sample between at least one workchamber using at least one sample handling device, said work chamberbeing configured for preparing said wafer sample for said chargedparticle beam imaging, or for said charged particle beam imaging step tobe performed therewithin.
 3. The method of claim 1, wherein said samplehandling device and at least one portion of said work chamber aregrounded at any given time point during said transfer-in andtransfer-out process.
 4. The method of claim 3, wherein said at leastone portion of said work chamber is in contact with said wafer sample.5. The method of claim 1 wherein said first, second and third samplehandling members, said pre-aligner; said platform of said loadingchamber, said support member and said securing unit have an electricalresistivity of 10⁵ to 10⁹ ohms-cm, or less than 10⁵ ohms-cm.
 6. Themethod of claim 1, wherein said securing unit comprises an electrostaticchuck (e-chuck).
 7. The method of claim 1, wherein said transfer-outprocess comprises: un-securing, after the step of said charged particlebeam imaging, said wafer sample on said support member using saidsecuring unit; picking said wafer sample from said support member usingsaid third sample handling member, transferring, using said secondsample handling member, said wafer sample from said third samplehandling member onto said platform of said loading chamber; andtransferring, using said first sample handling member, said wafer samplefrom said loading chamber into said wafer sample storage, wherein at anygiven time point during said transfer-out process, said wafer sample iscaused to be grounded by grounding said first, second and third samplehandling members, said loading chamber, said support member and saidsecuring unit.
 8. The method of claim 7, wherein said first, second andthird sample handling members, said pre-aligner, said platform of saidloading chamber, said support member and said securing unit have anelectrical resistivity of 10⁵ to 10⁹ ohms-cm, or less than 10⁵ ohms-cm.9. The method of claim 7, wherein said securing unit comprises anelectrostatic chuck (e-chuck).
 10. A computer readable medium encodedwith a computer program for controlling particle absorption on a wafersample during charged particle beam imaging, said Computer programexecuting the following actions: transferring, using a first samplehandling member, said wafer sample from a wafer sample storage onto asurface of a pre-aligner, said wafer sample storage being configured forpre-imaging and post-imaging storage of said wafer sample, saidpre-aligner being configured for, adjusting an angle of said wafersample; transferring, using said first sample handling member, saidwafer sample from said pre-aligner onto a platform of a loading chamber,said loading chamber being configured for preparing said wafer samplefor said charged particle beam imaging; picking said wafer sample withinsaid loading chamber using a second sample handling member;transferring, using a third sample handling member, said wafer samplefrom said second sample handling member onto a surface of a supportmember disposed within an inspection chamber for supporting said wafersample thereon during said charged particle beam imaging, said supportmember being equipped with a securing unit for securing and un-securingsaid wafer sample on said support member; securing said wafer sample onsaid support member using said securing unit; performing said chargedparticle beam imaging of said wafer sample; un-securing said wafersample; picking said wafer sample from said support member using saidthird sample handling member; transferring, using said second samplehandling member, said wafer sample from said third sample handlingmember onto said platform of said loading chamber; and transferring,using said first sample handling member, said wafer sample from saidloading chamber into said wafer sample storage, wherein at any giventime point other than said charged particle beam imaging step, saidwafer sample is kept electrically neutral by grounding said first,second and third sample handling members, said pre-aligner, said loadingchamber, said support member and said securing unit.
 11. The computerreadable medium of claim 10, wherein said first, second and third samplehandling members, said pre-aligner, said platform of said loadingchamber, said support member and said securing unit have an electricalresistivity of 10⁵ to 10⁹ohms-cm, or less than 10⁵ ohms-cm.
 12. Thecomputer readable medium of claim 10, wherein said wafer sample storagecomprises one selected from a group consisting of the following, or anycombination thereof: cassette, standard mechanical interface (SMIF),front opening unified pod (FOUP).
 13. The computer readable medium ofclaim 10, wherein said first sample handling member comprises a robotend effecter.
 14. The computer readable medium of claim 10, wherein saidthird sample handling member comprises at least one projectionswhereupon said wafer sample is seated.
 15. The computer readable mediumof claim 10, wherein said loading chamber comprises a load lock.
 16. Acharged particle beam imaging system of a wafer sample, comprising: acharged particle beam generator for generating a primary chargedparticle beam; a condenser lens module for condensing said primarycharged particle beam; a probe forming objective lens module forfocusing condensed said primary charged particle beam into a chargedparticle beam probe; a charged particle beam deflection module forscanning said charged particle beam probe across a surface of said wafersample; a secondary charged particle detector module for detectingcharged particles generated from said wafer sample surface when beingbombarded by said charged particle beam probe, and whereby generating asecondary charged particle detection signal accordingly; an imageforming module electrically coupled with said secondary charged particledetector module for receiving said secondary charged particle detectionsignal from said secondary charged particle detector module and formingat least one charged particle microscope image; and a particlecontamination controller coupled with a first sample handling member, asecond sample handling member and a third sample handling member fortransferring said wafer sample, a wafer sample storage for pre-imagingand post-imaging storage of said wafer sample; a pre-aligner foradjusting an angle of said wafer sample, a loading chamber for preparingsaid wafer sample for said charged particle beam imaging, and a supportmember disposed within an inspection chamber for supporting said wafersample thereon during said charged particle inspection, said supportmember being equipped with a securing unit for securing and un-securingsaid wafer sample on said support member, said particle contaminationcontroller comprising a computer readable medium encoded with a computerprogram for controlling particle absorption on a wafer sample duringcharged particle beam imaging, wherein said computer program performsthe following steps: transferring, using said first sample handlingmember, said wafer sample from said wafer sample storage onto a surfaceof said pre-aligner, transferring, using said first sample handlingmember, said wafer sample from said pre-aligner onto a platform of saidloading chamber; picking said wafer sample within said loading chamberusing said second sample handling member; transferring, using said thirdsample handling member, said wafer sample from said second samplehandling member onto a surface of said support member; securing saidwafer sample on said support member using said securing unit; performingsaid charged particle beam imaging of said wafer sample; un-securingsaid wafer sample; picking said wafer sample from said support memberusing said third sample handling member; transferring, using said secondsample handling member, said wafer sample from said third samplehandling member onto said platform of said loading chamber; andtransferring, using said first sample handling member, said wafer samplefrom said loading chamber into said wafer sample storage, wherein at anygiven time point other than said charged particle beam imaging step,said wafer sample is kept electrically neutral by grounding said first,second and third sample handling members, said-pre-aligner, said loadingchamber, said support member and said securing unit.
 17. The chargedparticle beam imaging system of claim 16, wherein said first, second andthird sample handling members, said pre-aligner, said platform of saidloading chamber, said support member and said securing unit have anelectrical resistivity of 10⁵ to 10⁹ ohms-cm, or less than 10⁵ ohms-cm.18. The charged particle beam imaging system of claim 16, wherein saidwafer sample storage comprises one selected from a group consisting ofthe following, or any combination thereof: cassette, standard mechanicalinterface (SMIF), front opening unified pod (FOUP).
 19. The chargedparticle beam imaging system of claim 16, wherein said securing unitcomprises an electrostatic chuck (e-chuck).